Principal Parts: How to Learn a Verb

When you learn an English verb you often need three forms: sing – sang – sung, go – went – gone. German works the same way, but with one extra piece that English does not have — and forgetting it is the reason so many learners build grammatically broken perfect tenses. This page shows you exactly what to store in your memory for every new verb, so that you never have to guess.

The four principal parts

The principal parts (German: Stammformen) are the minimal set of forms from which every other form of a verb can be derived. For German there are four:

1. The infinitive — the dictionary form: gehen (to go).
2. The third-person Präteritum — the simple-past stem: ging (went).
3. The past participle — used in the Perfekt and passive: gegangen (gone).
4. The auxiliary — haben or sein, the helper verb the participle pairs with.

The conventional way to write them, the way dictionaries and reference tables do, includes the auxiliary right there with the participle:

gehen – ging – ist gegangen

That little ist is doing essential work: it tells you the verb forms its Perfekt with sein, not haben. Compare:

sehen – sah – hat gesehen (to see; takes haben)

Why the auxiliary is a principal part

This is the insight most courses skip. English speakers are used to perfect tenses always using "have": I have gone, I have seen, I have stayed. So they assume German participles all pair with haben and learn only the participle. The result is consistently wrong perfects for a whole class of verbs.

German chooses between haben and sein based on the meaning of the verb (broadly: verbs of motion-to-a-place and change-of-state take sein; most others take haben). The choice is not predictable from the participle's shape — gegangen and gegessen look completely parallel, yet one takes sein and the other haben:

Because you cannot derive the auxiliary later from the other forms, it has to be stored with the verb from the start. That is precisely why dictionaries print ist gegangen and not just gegangen.

Weak verbs: predictable, so almost free

For weak (regular) verbs, the principal parts follow a fixed recipe, so you barely have to memorize anything beyond the infinitive and the auxiliary:

• Präteritum = stem + -te
• Past participle = ge-
  • stem + -t
• Auxiliary = almost always haben

So machen gives you everything automatically:

machen – machte – hat gemacht (to do/make)

For weak verbs, then, the only genuinely new information per verb is the meaning and — in the rare cases it deviates — the auxiliary.

Strong verbs: all four must be memorized

For strong (irregular) verbs, none of the forms is fully predictable. The vowel changes in unpredictable ways (the ablaut), the participle ends in -en rather than -t, and the auxiliary may be either. You must memorize all four parts as a unit — there is no shortcut here, and any course that pretends otherwise is misleading you.

Note that gehen and fahren take sein (motion to a destination), while sehen takes haben — exactly the unpredictable choice the auxiliary captures.

The fifth piece: the present-tense vowel change

Many strong verbs also shift their stem vowel in the du and er/sie/es forms of the present tense — and this is not recoverable from the four parts above, so treat it as a fifth piece to store. The two common shifts are a → ä and e → i/ie.

So for fahren, the complete memory entry is really:

fahren – (du fährst, er fährt) – fuhr – ist gefahren

(liest, from lesen, shows the e → ie shift.) For weak verbs this fifth piece is empty — there is no stem-vowel change — which is one more reason weak verbs are so light to learn.

Common Mistakes

Key Takeaways

• Store four parts for every verb: infinitive, Präteritum, past participle, and the auxiliary (haben/sein).
• The auxiliary is genuinely unpredictable from the other forms, so it must be learned with the verb — that is why dictionaries write ist gegangen.
• Weak verbs are predictable (machen – machte – hat gemacht); strong verbs must be memorized in full (gehen – ging – ist gegangen).
• Add a fifth piece for strong verbs with a present-tense vowel change: fahren – du fährst.